1 Thessalonians 4:13 does not tell believers not to grieve. It says "sorrow not, even as others which have no hope." The distinction is not between grieving and not grieving — it is between grief with hope and grief without it. Paul's word for "sorrow" — lupesthe — is the ordinary Greek word for grief and pain. He does not forbid it. He locates it inside a framework: the same God who raised Jesus will raise those who died in him. The hope does not remove the grief. It holds it differently.
Lamentations 3:32 — "But though he cause grief, yet will he have compassion according to the multitude of his mercies" — was written from inside genuine disaster, the destruction of Jerusalem. The author does not explain why God allowed the loss. He holds two truths together: the grief is real, and compassion is what God moves toward. This is not a comfortable theology. It is an honest one, written by someone who had actually lost everything.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.